It is becoming increasingly more common to utilize automatic electric circuit breakers to serve various auxiliary functions in addition to their traditional circuit protective role. This trend is most pronounced with higher current rated, industrial circuit breakers, but now is increasingly being evidenced in applications calling for the lower current rated, residential type circuit breakers. Such auxiliary functions typically fall into two general categories; one being an "operating" function of which remote or shunt trips are the most common example, and the other being an "indicating" function best exemplified by trip alarms.
For those installations calling for residential type circuit breakers, it is now common practice as illustrated in U.S. Pat. No. 3,256,407, to house the accessory device in a dummy or accessorial molded circuit breaker case affixed in side-by-side relation with a circuit breaker housed in a similarly configured molded case. This is done, quite simply, because there is typically no room within the circuit breaker case to accommodate accessory devices. Additional, identical molded case circuit breakers may be added in side-by-side relation for two and three-pole installations. The accessory device in its case is operatively connected with the circuit breaker or breakers by an internal common trip bar. Additionally, the accessorial case is equipped with an external handle which is forced to follow the positionings of the circuit breaker operating handle(s) via an external handle tie.
In the trip alarm adaptation, a conventional, off-the-shelf microswitch is positioned in the accessorial case and is adapted to be actuated either directly or indirectly via the internal common trip bar incident to automatic operation of one of the circuit breakers to effect circuit interruption in response to an overcurrent condition. This switch controls an indicator or alarm circuit to manifest at a remote location the fact that a circuit breaker or circuit breakers have tripped. Alternatively, the switch may be actuated in response to movement of the accessorial case handle from its ON position to its tripped or OFF position.
In a typical implementation, the accessorial case includes a dummy circuit breaker operating mechanism. The common trip bar extending into the accessorial case is normally effective to maintain this dummy operating mechanism in a latched condition, such that its contact arm assumes a first position corresponding to the closed circuit positions of the contact arms of the adjacent circuit breakers when the ganged operating handles are manipulated to their ON positions. When one of the circuit breakers trips, all of the operating mechanisms, including the dummy operating mechanism, are unlatched, and the dummy movable contact arm moves to a second position corresponding to the OFF positions of the circuit breaker contact arms. In this second position, the dummy contact arm actuates the indicating circuit microswitch. Similarly, if the ganged operating handles are moved to their OFF positions, the operating handle in the accessorial case shifts the dummy contact arm to its second position to again actuate the microswitch.
In the shunt trip adaptation, a trip solenoid is incorporated in the accessorial case, such that upon energization its solenoid strikes the internal common trip bar or some extension thereof to trip all of the circuit breakers common thereto. It is common practice to incorporate a switch within the accessorial case to interrupt the solenoid energization circuit once tripping of the circuit breakers has been achieved. In this way, the trip solenoid is not required to carry continuous energizing current and thus can be of a light duty, inexpensive design. In practice, this trip solenoid de-energizing switch has taken the form of a conventional, off-the-shelf microswitch actuated from the common trip bar.
These miniature switches or microswitches utilized in trip alarm and shunt trip accessory devices add significantly to the expense of implementing these auxiliary functions. Moreover, unless of particularly high quality, these miniature switches are not particularly long-lived. Also, the practice of utilizing dummy circuit breaker parts solely for the purpose of achieving a switching function adds undue cost and complexity to the design of such accessory devices.
It is accordingly an object of the present invention to provide improved circuit breaker accessory devices for implementing various auxiliary functions.
A further object of the present invention is to provide accessory devices of the above character which utilize an improved auxiliary switch.
A further object is to provide an auxiliary switch of the above character requiring a minimum number of parts.
Yet another object of the present invention is to provide an auxiliary switch of the above character which is simple in design, inexpensive to manufacture and reliable in operation.
Other objects of the invention will in part be obvious and in part appear hereinafter.